1. Field of the Invention
The present invention relates to shift controls for manual change gear transmissions and in particular to shift controls for manual change gear transmissions, or transmission sections, having shift bar assemblies comprising at least three shift rails with the highest gear reduction forward speed (i.e., low gear) and reverse speed engaged by axial movement of separate adjacent shift rails.
2. Description of the Prior Art.
Manually shifted change gear transmissions utilizing shift bar assemblies comprising a plurality of generally parallel shift bars or rails, each of which rails carries a shift fork for axial movement therewith and which is axially movable from a neutral position in one or two axial directions to engage and disengage one or two selected gear ratios are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,120,212; 4,304,144 and 3,998,110, the disclosures of all of which are hereby incorporate by reference. Such shift bar housing assemblies typically comprise an outer shift rail which is associated with reverse and/or low gear and a resilient detent or lockout mechanism which must be overcome or released to select the rail to prevent inadvertent selection thereof. Examples of such detent and lockout mechanisms may be seen by reference to U.S. Pat. Nos. 3,541,879; 3,866,488 and 3,937,100, the disclosures of all of which are hereby incorporated by reference.
While such prior art mechanisms are well known and widely commercially utilized, they are not satisfactory for a transmission having two adjacent shift rails, one associated with the reverse speed or speeds and the other with the low forward speed or speeds ratios to prevent inadvertent selection of both shift rails.